An electromagnetic pickup (pickup, hereinafter) converts the vibrations of plucked strings of an electric guitar, which are located on top of the pickup where electromagnetic fields are formed, into an electrical signal. In general a single coil pickup (SC pickup, hereinafter) comprises of a set of pole pieces made of magnetic or ferromagnetic materials, magnetic wire coil, bobbin plates, and lead wires. The SC pickup is sensitive to external magnetic fields created by speakers, power transducers, fluorescent light sources and so on, resulting in undesired humming noise.
Such humming noise can be reduced or eliminated by combining two magnetic sensing coils electrically out-of-phase so that two signals generated by the external sources can be cancelled each other. The electromagnetic signal from guitar strings can be preserved either by setting the two coils magnetically out-of-phase or by isolating one of the two coils magnetically from the strings.
Overall, there are two structural configurations—1) side-by-side configuration, wherein two coils are situated side-by-side and are both electrically and magnetically out-of-phase (U.S. Pat. No. 2,896,491, U.S. Pat. No. 4,364,295, U.S. Pat. No. 4,372,186, U.S. Pat. No. 4,501,185, U.S. Pat. No. 5,111,728, U.S. Pat. No. 5,525,750, U.S. Pat. No. 5,530,199, U.S. Pat. No. 8,309,836, US Pat. Appl. No. US 2012/0103170, and so on), and 2) stacked configuration, wherein two coils are stacked on top of each other and are both electrically and magnetically out-of-phase like the former (U.S. Pat. No. 6,846,981), or electrically out-of-phase and magnetically in-phase with magnetic isolating means for one coil (U.S. Pat. No. 4,442,749, U.S. Pat. No. 5,168,117, U.S. Pat. No. 5,668,520, U.S. Pat. No. 5,811,710, U.S. Pat. No. 6,103,966, U.S. Pat. No. 6,291,758, U.S. Pat. No. 6,291,759, U.S. Pat. No. 6,846,981, U.S. Pat. No. 7,166,793, U.S. Pat. No. 7,189,916, and so on).
The most popular hum-cancelling pickup with the side-by-side configuration was introduced by Lover (U.S. Pat. No. 2,896,491). The pickups built according to this invention have been called PAF (Patent Applied For), which was printed on the bottom plate of those pickups in the early days. In this document the hum-cancelling pickup with the side-by-side configuration is referred to simply as the HB (Hum-Bucking) pickup, hereinafter. It is to be noted that the hum-cancelling pickup with the stacked configuration will be referred to as the stacked hum-cancelling pickup.
A pickup has a unique response characteristic to string vibrations resulting in a unique tone color. Pickup tone is dependent on many parameters, which include magnet materials, pole pieces, bobbin materials and structures, magnet wire gage, magnet wire coating materials, the number of wire turns and so on. Although external factors such as guitar builds, effects pedals and amplifiers can color the tone characters to some extent, they cannot completely override the original tone of the pickup. That is why old classical pickups including the said PAF are still popular, and also, a number of different pickup products are available in the music industry.
Two most distinctive tone colors are generated from aforementioned SC and HB pickups. The SC pickup usually produces a clear and bright sound with a focus on the treble to mid-range domain, whereas the HB pickup produces a warm and thick sound with a focus on the mid-range domain. The majority of electric guitar players use both types of pickups depending on the needs. Because it is inconvenient and impractical to change guitars for different pickup sounds in the middle of performance, many guitar builders and pickup makers offer the option of “coil-splitting”, by which a guitar player can use only one of the two coils in the HB pickup, or more rarely “combining”, in which two individual SC pickups are electrically connected like one HB pickup. However, both methods do not deliver a purposed SC or HB sound very well. A coil-split pickup sound is typically thinner and less lively than a genuine SC pickup sound. On the other hand, a combination of two genuine SC pickups does not usually produce a good HB pickup sound defined by warmth and fullness. As a result, pickups that can produce both HB and SC sounds are hardly found.
From a set of experiments it was found that one of the most critical factors, which make the difference in sound characteristics between a genuine SC pickup and a coil-split HB pickup, was the space between the coil and the pole pieces and that such space in the HB pickup can be made closer to that of the SC pickup without damaging or changing the sound characteristics and form factor of the HB pickup. The details of this invention and embodiments are described in the next sections.